1. Field of the Invention
This invention generally relates to integrated circuits, and more particularly to executing an electrical function, such as a fusing operation, in an integrated circuit and to a method of manufacture thereof.
2. Background Art
Fuses and antifuses are programmable electronic devices that are used in a variety of circuit applications. A fuse is normally closed, and when blown or programmed results in an “open” or increase in resistance. An antifuse is similar to a fuse in that it is programmable. However, an antifuse is normally open, having a capacitor-like structure. When an antifuse is blown or programmed, this results in a short, or decreased resistance.
There are many applications for fuses and antifuses. One particular application in integrated circuits is to improve yields using redundancy. By providing, for example, redundant memory cells on memory chips, the circuits or modules that are defective or not needed may be eliminated from circuit operation, thus improving the yield. This may be accomplished by programming fuses or antifuses to alter, disconnect or bypass active cells or circuits and allow redundant memory cells to be used in place of cells that are not functional. Similarly, information may be rerouted using fuses and/or antifuses.
Another exemplary application for fuses and antifuses is for customizing integrated circuits (IC's) after production. One IC configuration may be used for multiple applications by programming the fuses and/or antifuses (e.g., by blowing or rupturing selected fuses and antifuses) to deactivate and select circuit paths. Thus, a single integrated circuit design may be economically manufactured and adapted for a variety of custom uses.
Fuses and antifuses may also be used to program chip identification (ID) after an integrated circuit is produced. A series of ones and zeros can be programmed in to identify the IC so that a user will know its programming and device characteristics, as examples.
Typically, fuses or fusible links are incorporated into an integrated circuit design, and then these fuses or fusible links are selectively programmed, e.g., blown or ruptured, by passing an electrical current of sufficient magnitude through the selected fuses to cause them to melt and break the connection.
It is thus desirable to enhance yield of integrated chips by including redundant elements that could replace some specific faulty circuits or components on the chip following testing after fabrication. It is also equally important to have the means to repair failing chips during normal field operation by replacing some failing parts of the chip with redundant elements, thus in effect improving overall reliability and serviceability.
In technologies employing optical imaging sensors, the enhancement of yield and reliability can be done by incorporating the features of the technology regarding optical detection. One specific example pertaining to optical imaging technologies is the extensive use of capacitors for charge integration. These capacitors, with large amount could have an effect on yield and reliability and thus having redundant capacitor circuits that could be implemented to hardware before shipment to customers, and providing repair during usage would be very beneficial. Such implementation of redundant elements for both yield and reliability normally requires additional pins at the package level where programming, to execute implementation of repair, could be performed at the package level. In many applications and designs, it is not convenient or possible to have additional pins at the package level for such implementation.